Inorganic nanoparticles, such as superparamagnetic iron oxide nanoparticles (SPIONs), have various potential biomedical applications, including imaging applications, magnetic resonance imaging (MRI), sensing, and drug delivery. Such applications require nanoparticles that are hydrophilic and biocompatible. Appropriate surface derivatization can provide inorganic nanoparticles with the necessary hydrophilicity. Preferably the nanoparticles remain stable in aqueous solution, have a low level of non-specific protein binding, and a small hydrodynamic diameter.